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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_TRACING_CORE_PROTO_ZERO_MESSAGE_HANDLE_H_
#define COMPONENTS_TRACING_CORE_PROTO_ZERO_MESSAGE_HANDLE_H_
#include "base/macros.h"
#include "components/tracing/tracing_export.h"
namespace tracing {
namespace v2 {
class ProtoZeroMessage;
// ProtoZeroMessageHandle allows to decouple the lifetime of a proto message
// from the underlying storage. It gives the following guarantees:
// - The underlying message is finalized (if still alive) if the handle goes
// out of scope.
// - In Debug / DCHECK_ALWAYS_ON builds, the handle becomes null once the
// message is finalized. This is to enforce the append-only API. For instance
// when adding two repeated messages, the addition of the 2nd one forces
// the finalization of the first.
// Think about this as a WeakPtr<ProtoZeroMessage> which calls
// ProtoZeroMessage::Finalize() when going out of scope.
class TRACING_EXPORT ProtoZeroMessageHandleBase {
public:
~ProtoZeroMessageHandleBase();
// Move-only type.
ProtoZeroMessageHandleBase(ProtoZeroMessageHandleBase&& other);
ProtoZeroMessageHandleBase& operator=(ProtoZeroMessageHandleBase&& other);
protected:
explicit ProtoZeroMessageHandleBase(ProtoZeroMessage*);
ProtoZeroMessage& operator*() const { return *message_; }
ProtoZeroMessage* operator->() const { return message_; }
private:
friend class ProtoZeroMessage;
void reset_message() { message_ = nullptr; }
void Move(ProtoZeroMessageHandleBase* other);
ProtoZeroMessage* message_;
DISALLOW_COPY_AND_ASSIGN(ProtoZeroMessageHandleBase);
};
template <typename T>
class ProtoZeroMessageHandle : ProtoZeroMessageHandleBase {
public:
explicit ProtoZeroMessageHandle(T* message)
: ProtoZeroMessageHandleBase(message) {}
T& operator*() const {
return static_cast<T&>(ProtoZeroMessageHandleBase::operator*());
}
T* operator->() const {
return static_cast<T*>(ProtoZeroMessageHandleBase::operator->());
}
};
} // namespace v2
} // namespace tracing
#endif // COMPONENTS_TRACING_CORE_PROTO_ZERO_MESSAGE_HANDLE_H_
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